Spice Model software

[John]

I am told that there is software which can create a spice model from the
data contained in a typical transistor datasheet. Does anyone have such
software and if so does it produce worthwhile model data ?

If the software is in the public domain is there a chance I could get a copy
from someone ?

Thanks,
John

 

[Chaos Master]

John bleeding:

I am told that there is software which can create a spice model from the
data contained in a typical transistor datasheet. Does anyone have such
software and if so does it produce worthwhile model data ?

The term for this is "model characterization". I'd love to have one of those
programs. But they're expensive.

The ones I remember seeing are PSpice Parts, and MODPEX.

PSpice Parts is expensive as it is part of the PSpice package.
MODPEX is even more expensive, and AFAIK it only runs on high-end workstations.

Intusoft also makes a tool for model characterization but I can't recall the
name.

If the software is in the public domain is there a chance I could get a copy
from someone ?

It is not in the public domain. :/

 

[qrk]

I am told that there is software which can create a spice model from the
data contained in a typical transistor datasheet. Does anyone have such
software and if so does it produce worthwhile model data ?

If the software is in the public domain is there a chance I could get a copy
from someone ?

Thanks,
John

PSpice has this capability. Some report that it sucks though. If you
can't find spice data on the web, sometimes you can email the
manufacturer and get spice models.

 

[Charles Edmondson]

I am told that there is software which can create a spice model from the
data contained in a typical transistor datasheet. Does anyone have such
software and if so does it produce worthwhile model data ?

If the software is in the public domain is there a chance I could get a copy
from someone ?

Thanks,
John

The PSpice Model Editor allows for this sort of thing, but it isn't
cheap as it is part of the PSpice program. Now, if Mike should add this
capability to LTSpice, that could be really helpful.

Often, users and vendors literally create a test bench of the part to
characterized with all the attributes visible on the schematic, and the
appropriate loads and sources. You then tweak all the values while
looking at the output curves, until they match the required response.
It isn't easy or fast, and requires a good deal of knowledge about the
modeling process, but it gets the job done.

 

[Jim Thompson]

The PSpice Model Editor allows for this sort of thing, but it isn't
cheap as it is part of the PSpice program. Now, if Mike should add this
capability to LTSpice, that could be really helpful.

Often, users and vendors literally create a test bench of the part to
characterized with all the attributes visible on the schematic, and the
appropriate loads and sources. You then tweak all the values while
looking at the output curves, until they match the required response.
It isn't easy or fast, and requires a good deal of knowledge about the
modeling process, but it gets the job done.

Hi Charlie,

As you know I've never been enamored of the PSpice Model Editor. Feed
it data and create a model. Take data on that model and feed to the
Editor, get a NEW model :-(

...Jim Thompson

 

[Charles Edmondson]

Hi Charlie,

As you know I've never been enamored of the PSpice Model Editor. Feed
it data and create a model. Take data on that model and feed to the
Editor, get a NEW model :-(

...Jim Thompson

Hi Jim,
Yep, the joys of computer extraction! It is always interesting when
there are questions on models, esp. some of the new BSIM models. I have
had several students say "We need a generic BSIMx.x model, can you help
us?" The problem is that, these models are not unique! So many of the
parameters interact in 'interesting' ways, that you can two models with
very, very different values, that simulate with exactly the same results!

As with all things with models, make sure it models the effects you
want. A generic Cap model will not model ESR or the failure modes of a
tantalum. Most opamp models don't model power supply drain. If a model
exhibits the behavior you need well enough, then use it!

Charlie

 

[Mantra]

Yep, the joys of computer extraction! It is always interesting when
there are questions on models, esp. some of the new BSIM models. I have
had several students say "We need a generic BSIMx.x model, can you help
us?" The problem is that, these models are not unique! So many of the
parameters interact in 'interesting' ways, that you can two models with
very, very different values, that simulate with exactly the same results!

As with all things with models, make sure it models the effects you
want. A generic Cap model will not model ESR or the failure modes of a
tantalum. Most opamp models don't model power supply drain. If a model
exhibits the behavior you need well enough, then use it!

Just so. A model is an abstraction that allows you to predict future
behavior. A good model simply predicts well enough to allow you
ignore what it doesn't predict.

Most device models are lower or higher order that real life devices,
which means that the equations will be under- or over-specified when
you try to match simulation to live measurements. In the
underspecified case, the simulation will only "match well" for a
handful of bias points. In the overspecified case (BSIM models
typically), the simulation will "match well" over many non-unique
parameter value sets - which is actually a more insidious situation.
The only way to get around either is to "know" the model and "know"
your simulation/design conditions so you can plan the extraction well.

As for "extracting a model from a datasheet", in most cases the
datasheet parameters are geared toward *hand-design* rather than
simulator design. For example the typical specs on a BJT are barely
sufficient to define even the basic Ebers-Moll BJT model, though you
can bootstrap the JFET model with typical JFET datasheet specs. If
you are doing transistor level design, you should be starting with a
hand-design anyway.

 

[John]

The PSpice Model Editor allows for this sort of thing, but it isn't
cheap as it is part of the PSpice program.
Now, if Mike should add this capability to LTSpice, that could be really

helpful.


How about it Mike ?